/*
 *                    GNU LESSER GENERAL PUBLIC LICENSE
 *                        Version 3, 29 June 2007
 *
 *  Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
 *  Everyone is permitted to copy and distribute verbatim copies
 *  of this license document, but changing it is not allowed.
 *
 *
 *   This version of the GNU Lesser General Public License incorporates
 * the terms and conditions of version 3 of the GNU General Public
 * License, supplemented by the additional permissions listed below.
 *
 *   0. Additional Definitions.
 *
 *   As used herein, "this License" refers to version 3 of the GNU Lesser
 * General Public License, and the "GNU GPL" refers to version 3 of the GNU
 * General Public License.
 *
 *   "The Library" refers to a covered work governed by this License,
 * other than an Application or a Combined Work as defined below.
 *
 *   An "Application" is any work that makes use of an interface provided
 * by the Library, but which is not otherwise based on the Library.
 * Defining a subclass of a class defined by the Library is deemed a mode
 * of using an interface provided by the Library.
 *
 *   A "Combined Work" is a work produced by combining or linking an
 * Application with the Library.  The particular version of the Library
 * with which the Combined Work was made is also called the "Linked
 * Version".
 *
 *   The "Minimal Corresponding Source" for a Combined Work means the
 * Corresponding Source for the Combined Work, excluding any source code
 * for portions of the Combined Work that, considered in isolation, are
 * based on the Application, and not on the Linked Version.
 *
 *   The "Corresponding Application Code" for a Combined Work means the
 * object code and/or source code for the Application, including any data
 * and utility programs needed for reproducing the Combined Work from the
 * Application, but excluding the System Libraries of the Combined Work.
 *
 *   1. Exception to Section 3 of the GNU GPL.
 *
 *   You may convey a covered work under sections 3 and 4 of this License
 * without being bound by section 3 of the GNU GPL.
 *
 *   2. Conveying Modified Versions.
 *
 *   If you modify a copy of the Library, and, in your modifications, a
 * facility refers to a function or data to be supplied by an Application
 * that uses the facility (other than as an argument passed when the
 * facility is invoked), then you may convey a copy of the modified
 * version:
 *
 *    a) under this License, provided that you make a good faith effort to
 *    ensure that, in the event an Application does not supply the
 *    function or data, the facility still operates, and performs
 *    whatever part of its purpose remains meaningful, or
 *
 *    b) under the GNU GPL, with none of the additional permissions of
 *    this License applicable to that copy.
 *
 *   3. Object Code Incorporating Material from Library Header Files.
 *
 *   The object code form of an Application may incorporate material from
 * a header file that is part of the Library.  You may convey such object
 * code under terms of your choice, provided that, if the incorporated
 * material is not limited to numerical parameters, data structure
 * layouts and accessors, or small macros, inline functions and templates
 * (ten or fewer lines in length), you do both of the following:
 *
 *    a) Give prominent notice with each copy of the object code that the
 *    Library is used in it and that the Library and its use are
 *    covered by this License.
 *
 *    b) Accompany the object code with a copy of the GNU GPL and this license
 *    document.
 *
 *   4. Combined Works.
 *
 *   You may convey a Combined Work under terms of your choice that,
 * taken together, effectively do not restrict modification of the
 * portions of the Library contained in the Combined Work and reverse
 * engineering for debugging such modifications, if you also do each of
 * the following:
 *
 *    a) Give prominent notice with each copy of the Combined Work that
 *    the Library is used in it and that the Library and its use are
 *    covered by this License.
 *
 *    b) Accompany the Combined Work with a copy of the GNU GPL and this license
 *    document.
 *
 *    c) For a Combined Work that displays copyright notices during
 *    execution, include the copyright notice for the Library among
 *    these notices, as well as a reference directing the user to the
 *    copies of the GNU GPL and this license document.
 *
 *    d) Do one of the following:
 *
 *        0) Convey the Minimal Corresponding Source under the terms of this
 *        License, and the Corresponding Application Code in a form
 *        suitable for, and under terms that permit, the user to
 *        recombine or relink the Application with a modified version of
 *        the Linked Version to produce a modified Combined Work, in the
 *        manner specified by section 6 of the GNU GPL for conveying
 *        Corresponding Source.
 *
 *        1) Use a suitable shared library mechanism for linking with the
 *        Library.  A suitable mechanism is one that (a) uses at run time
 *        a copy of the Library already present on the user's computer
 *        system, and (b) will operate properly with a modified version
 *        of the Library that is interface-compatible with the Linked
 *        Version.
 *
 *    e) Provide Installation Information, but only if you would otherwise
 *    be required to provide such information under section 6 of the
 *    GNU GPL, and only to the extent that such information is
 *    necessary to install and execute a modified version of the
 *    Combined Work produced by recombining or relinking the
 *    Application with a modified version of the Linked Version. (If
 *    you use option 4d0, the Installation Information must accompany
 *    the Minimal Corresponding Source and Corresponding Application
 *    Code. If you use option 4d1, you must provide the Installation
 *    Information in the manner specified by section 6 of the GNU GPL
 *    for conveying Corresponding Source.)
 *
 *   5. Combined Libraries.
 *
 *   You may place library facilities that are a work based on the
 * Library side by side in a single library together with other library
 * facilities that are not Applications and are not covered by this
 * License, and convey such a combined library under terms of your
 * choice, if you do both of the following:
 *
 *    a) Accompany the combined library with a copy of the same work based
 *    on the Library, uncombined with any other library facilities,
 *    conveyed under the terms of this License.
 *
 *    b) Give prominent notice with the combined library that part of it
 *    is a work based on the Library, and explaining where to find the
 *    accompanying uncombined form of the same work.
 *
 *   6. Revised Versions of the GNU Lesser General Public License.
 *
 *   The Free Software Foundation may publish revised and/or new versions
 * of the GNU Lesser General Public License from time to time. Such new
 * versions will be similar in spirit to the present version, but may
 * differ in detail to address new problems or concerns.
 *
 *   Each version is given a distinguishing version number. If the
 * Library as you received it specifies that a certain numbered version
 * of the GNU Lesser General Public License "or any later version"
 * applies to it, you have the option of following the terms and
 * conditions either of that published version or of any later version
 * published by the Free Software Foundation. If the Library as you
 * received it does not specify a version number of the GNU Lesser
 * General Public License, you may choose any version of the GNU Lesser
 * General Public License ever published by the Free Software Foundation.
 *
 *   If the Library as you received it specifies that a proxy can decide
 * whether future versions of the GNU Lesser General Public License shall
 * apply, that proxy's public statement of acceptance of any version is
 * permanent authorization for you to choose that version for the
 * Library.
 *
 */

package vip.isass.core.support;

import cn.hutool.core.collection.CollUtil;
import cn.hutool.core.lang.Assert;
import cn.hutool.core.lang.tree.Tree;
import cn.hutool.core.lang.tree.TreeNodeConfig;
import cn.hutool.core.lang.tree.TreeUtil;
import cn.hutool.core.lang.tree.parser.NodeParser;
import cn.hutool.core.map.MapUtil;
import cn.hutool.core.util.ArrayUtil;
import cn.hutool.core.util.ReflectUtil;
import cn.hutool.core.util.StrUtil;
import vip.isass.core.entity.ChildrenEntity;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.function.Function;

/**
 * 列表转树结构工具
 */
public class TreeEntityUtil {

    /**
     * @param treeNodes treeNodes
     * @param function  function
     * @param <TE>      tree entity
     * @param <R>       return entity
     * @return List of R entity
     */
    private static <TE, R extends ChildrenEntity<R>> List<R> convertToTree(List<Tree<TE>> treeNodes,
                                                                           Function<Tree<TE>, R> function) {
        if (CollUtil.isEmpty(treeNodes)) {
            return Collections.emptyList();
        }
        List<R> list = new ArrayList<>(treeNodes.size());
        for (Tree<TE> treeNode : treeNodes) {
            R r = function.apply(treeNode);
            r.setChildren(convertToTree(treeNode.getChildren(), function));
            list.add(r);
        }
        return list;
    }

    /**
     * @param entities                 entities
     * @param parentId                 parentId
     * @param treeNodeConfig           treeNodeConfig
     * @param entityToTreeNode         entityToTreeNode
     * @param treeNodeToChildrenEntity treeNodeToChildrenEntity
     * @param <TE>                     tree entity
     * @param <E>                      source entity
     * @param <R>                      return entity
     * @return List of R entity
     */
    public static <TE, E, R extends ChildrenEntity<R>> List<R> convertToTree(List<E> entities,
                                                                             TE parentId,
                                                                             TreeNodeConfig treeNodeConfig,
                                                                             NodeParser<E, TE> entityToTreeNode,
                                                                             Function<Tree<TE>, R> treeNodeToChildrenEntity) {

        List<Tree<TE>> trees = TreeUtil.build(entities, parentId, treeNodeConfig, entityToTreeNode);
        return convertToTree(trees, treeNodeToChildrenEntity);
    }

    /**
     * @param entities                 entities
     * @param parentId                 parentId
     * @param entityToTreeNode         entityToTreeNode
     * @param treeNodeToChildrenEntity treeNodeToChildrenEntity
     * @param <TE>                     tree entity
     * @param <E>                      source entity
     * @param <R>                      return entity
     * @return List of R entity
     */
    public static <TE, E, R extends ChildrenEntity<R>> List<R> convertToTree(List<E> entities,
                                                                             TE parentId,
                                                                             NodeParser<E, TE> entityToTreeNode,
                                                                             Function<Tree<TE>, R> treeNodeToChildrenEntity) {

        return convertToTree(entities, parentId, TreeNodeConfig.DEFAULT_CONFIG, entityToTreeNode, treeNodeToChildrenEntity);
    }

    /**
     * 将 entityList 转为树形结构
     *
     * @param entityList         要转换的实体列表
     * @param idFieldName        id字段名
     * @param parentIdFieldName  parentId 字段名
     * @param childrenFieldName  children 字段名
     * @param topLevelIdValueArr 顶层实体的 id,当顶层实体的parentId不是 null 或空时，可以传此值指定顶级实体的 id，提高解析性能
     * @param <T>                实体类型
     * @return 树形结果
     */
    public static <T> List<T> convert(List<T> entityList,
                                      String idFieldName,
                                      String parentIdFieldName,
                                      String childrenFieldName,
                                      String... topLevelIdValueArr) {
        if (CollUtil.isEmpty(entityList)) {
            return Collections.emptyList();
        }

        Assert.notBlank(idFieldName, "idFileName 必填");
        Assert.notBlank(parentIdFieldName, "parentIdFieldName 必填");
        Assert.notBlank(childrenFieldName, "childrenFieldName 必填");
        List<String> topLevelIdValues = ArrayUtil.isEmpty(topLevelIdValueArr)
            ? Collections.emptyList()
            : Arrays.asList(topLevelIdValueArr);

        // 用于保存当前 id 索引的实体类
        Map<String, T> entityMap = MapUtil.newHashMap(entityList.size());

        // 暂存区, 用于保存没有找到父 id 的控件
        List<T> tempList = new ArrayList<>();

        List<T> result = new ArrayList<>();

        for (T entity : entityList) {
            String id = Optional.ofNullable(ReflectUtil.getFieldValue(entity, idFieldName)).map(Object::toString).orElse("");
            Assert.notBlank(id, "存在主键为空的实体");
            entityMap.put(id, entity);

            String parentId = Optional.ofNullable(ReflectUtil.getFieldValue(entity, parentIdFieldName)).map(Object::toString).orElse("");
            if (StrUtil.isBlank(parentId) || topLevelIdValues.contains(id)) {
                // 如果父 id 为空, 或者 topLevelIdValues 包含 id， 则实体类为第一层
                result.add(entity);
            } else {
                // 查找父类实体
                T parentEntity = entityMap.get(parentId);
                if (parentEntity == null) {
                    // 没找到父类，先放入暂存区
                    tempList.add(entity);
                } else {
                    // 把实体放到父类的 childrenList
                    setChildrenValue(parentEntity, childrenFieldName, entity);
                }
            }
        }

        // 处理暂存区，找到其父类
        for (T entity : tempList) {
            // 获取 parentId
            String parentId = Optional.ofNullable(ReflectUtil.getFieldValue(entity, parentIdFieldName)).map(Object::toString).orElse("");

            // 根据父id获取实体类
            T parentEntity = entityMap.get(parentId);
            if (parentEntity == null) {
                result.add(entity);
            } else {
                // 把实体放到父类的 childrenList
                setChildrenValue(parentEntity, childrenFieldName, entity);
            }
        }
        return result;
    }

    @SuppressWarnings("unchecked")
    private static <T> void setChildrenValue(T parentEntity, String childrenFieldName, T entity) {
        Object children = ReflectUtil.getFieldValue(parentEntity, childrenFieldName);
        List<T> childrenList;
        if (children == null) {
            childrenList = new ArrayList<>();
            ReflectUtil.setFieldValue(parentEntity, childrenFieldName, childrenList);
        } else {
            childrenList = (List<T>) children;
        }
        childrenList.add(entity);
    }

}
